- ➊ Blacken some cells of the diagram [paper] resp. color the
gray cells of the diagram black or white [interactively].
- ➋ The black cells divide the diagram in areas of
orthogonally contiguous white cells.
- ➌ The white areas must not touch each other
- ➍ All cells with a number belong to a white area; to a white
area belongs exactly one cell with a number. The number indicates how many
cells belong to the white area.
- ➎ The black cells must not cover an area of 2x2 cells or
larger and must form an
orthogonally contiguous area.